A solar heat power generation system is known that condenses solar light in a heat collection area to collect heat, generates water vapor by the collected heat to drive a steam turbine, and generates power. In the solar heat power generation system, a heat storage system is provided in general in order to supplement the power generation at night or during a period of time in which sufficient solar radiation cannot be obtained, and also to suppress the transitional variance in an output power.
As the heat storage system used for the solar heat power generation system or the like, it is known to use, as a heat storage material, a molten salt in a liquid state, which is so called solar salt (e.g., a mixture of potassium nitrate (KNO3) and sodium nitrate (NaNO3), a mass fraction of sodium nitrate of 0.6), and to store heat by employing sensible heat (for example, see Patent Literature 1).
However, when a quantity (capacity) of heat storage becomes greater, for example, 1TJ, the required heat storage tank becomes too larger in the heat storage system employing the sensible heat so that such too large heat storage tank is no more realistic. To cope with this, in order to keep the realistic dimension of the heat storage system employing the sensible heat, it is desired to have a heat storage system employing latent heat instead.